Patent GB-845131-A (GB)
Title: A process and apparatus for the aftertreatment of chemical substances
IPC: B01D25/00
Filed: 1957-12-03
Abstract: 845,131. Filters; systems of filtration. MULLER, H. K. Dec. 3, 1957 [Dec. 7, 1956; Jan. 8, 1957 ; May 13, 1957], No. 37698/57. Class 46. In the after-treatment of chemical substances which have been separated out from their carrier liquid as residues by filtration, the residues are loosened from the filter elements by centrifugal force, a fresh supply of liquid is added to them to take up at least part of the residues, and the liquid and the residues taken up by it - are discharged into one or more containers connected to the filter, are subsequently returned to the filter after carrying out one or more chemical reactions or physical treating steps in the containers, and are finally filtered off. "Taking up" may be as a suspension or solution. In one process mixture from one (e.g. 19) of the containers 19 to 22 is withdrawn through valve 8 by pump 23 and forced at 4 (valve 15 being closed) into a casing 1, filtrate flowing out at 5 into another of the containers. After filtration the filter elements 3 are rotated to remove the residues centrifugally, optionally with the assistance of gas or liquid means. Next, washing liquid from container 20 is passed through the filter, the driving motor 24 being switched on and off periodically, and finally returned to 20. Then liquid in which the residues are to be suspended is pumped from container 21 to the filter, the filter elements being rotated meanwhile, the suspension finally being returned to container 21 (or another container) by reverse running of pump 23 or by gas under pressure. In the maunfacture of dyestuffs a diazo coupling and precipitation reaction may be carried out in one of the containers to which a suspension of an intermediate product has been passed from the filter. Reagents, and ice to keep the mixture cool, are added to the container. Such reactions may take place in the filter itself. In a re-crystallizing process suspension from container 19 is cyclically filtered until a clear filtrate is obtained in container 19. Liquid remaining in the filter 1 is forced back into 19 through valves 18 and 7 by compressed air introduced at 32, other valves being closed, and the crystal residues remaining on the elements. Gas to dry the crystals is now forced through valve 6 and pipe 5, and then they are washed by liquid from container 20. The filter is emptied of liquid and the crystals dried again, as before. Hot liquid from container 21 is next introduced in to the filter to re-dissolve the crystals, further heat being provided by a steam jacket 23. The solution is thereafter cooled and re-crystallized (either in the filter or in container 21) and again filtered and washed. The crystals are dried by air, optionally hot, supplied at 30, or by vacuum applied at 29 or 5. Finally the crystals are centrifuged off the elements, gas is supplied at a nozzle 26 from a pipe 25, and the crystals are discharged at 28 by a gas injector 34. In a countercurrent extraction process the first filtrate (extract), from mixture supplied in the first instance from container 19, is received in container 20. A second extraction is carried out from container 21, the extract being passed to container 20. Pure solvent from container 22 is used for a third extraction, the resulting extract passing to container 21 for further use. The contents of container 20 are withdrawn for further processing. The residue left in the filter after the extractions is removed by centrifuging. The apparatus may be used for repeated absorption and elution processes using an absorbent.